Yes, two S7150x2 cards are supported in the Dell R730. Just make sure to order the GPU kit with the system which provides the 6pin and 8pin power connectors for the cards. HP G8 will not work, G9 will be available soon. The cards use SR-IOV to handle the hardware virtualization, so the server must fully support SR-IOV in the SBIOS.
Currently ESXi 6.0u2 with Horizon View is officially supported. Most importantly, there is no licensing cost per VM.
More information is available here: http://www.amd.com/en-us/solutions/professional/virtualization
So a R730 will work at this moment ?
G9 will come later ? What is later ? Weeks, months ....